Within an hour or so, I received a great addition to surveys like this from Sarah McCambridge of Bishop Miege High School in Kansas. Sarah teaches photography, and she asks a simple but powerful question to her students at the end of each year: Please check any activity you found helpful.
Here's a screenshot of what a question like this spits out after students complete the Google Form:
Now there is a little work involved — we teachers would need to go back through our semester or school year and list within the form all the activities we did with students — but the data return is fabulous. An end-of-year survey task like this makes our student responses less dependent on their memories (which questions like “What's one thing Mr. Stuart did this year that helped you?” depend on heavily) or effort levels (because questions like “Which assignments helped you most?” force students to evaluate, and when they submit half-hearted answers to questions like these, it can mislead us to wrong conclusions about which of our assignments really helped best).
I encourage you to experiment with a question like Sarah's — I'm eager to as well.